ML20148J131
| ML20148J131 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 03/24/1988 |
| From: | LOUISIANA POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML20148J125 | List: |
| References | |
| NUDOCS 8803300180 | |
| Download: ML20148J131 (4) | |
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3/4.5 EMERGENCY CORE COOLING SYSTEMS (ECCS)
BASES 3/4.5.1 SAFETY INJECTION TANKS The OPERABILITY of each of the Reactor Coolant System (RCS) safety injection tanks ensures that a sufficient volume of borated water will be immediately forced into the reactor core through each of the cold legs in the event the RCS pressure falls below the pressure of the safety injection tanks.
This initial surge of water into the core provides the initial cooling mechanism during large RCS pipe ruptures.
The limits on safety injection tank volume, boron concentration, and pressure ensure that the assumptior.s used for safety injection tank injection in the safety analysis are met.
The safety injection tank power operated isolation valves are considered to be "operating bypasses" in the context of IEEE Std. 279-1971, which requires that bypasses of a protective function be removed automatically whenever permissive conditions are not met.
In addition, as these safety injection tank isolation valves fail to meet single failure criteria, removal of power to the valves is required.
The limits for operation with a safety injection tank inoperable for any reason except an isolation valve closed minimizes the time exposure of the plant to a LOCA event occuring concurrent with failure of an additional safety injection tank which may result in unacceptable peak cladding temperatures.
If a closed isolation valve cannot be immediately opened, the full capability of one safety injection tank is not available and prompt action is required to place the reactor in a mode where this capability is not required.
3/4.5.2 and 3/4.5.3 ECCS SUBSYSTEMS The OPERABILITY of two separate and independent ECCS subsystems ensures that sufficient emergency core cooling capability will be available in the event of a LOCA assuming the loss of one subsystem through any single failure consideration.
Either subsystem operating in conjunction with the safety injection tanks is capable of supplying sufficient core cooling to limit the peak cladding temp.eratures within acceptable limits for all postulated break sizes ranging from the double-ended break of the largest RCS cold leg pipe downward.
In addition, each ECCS subsystem provides long-term core cooling capability in the recirculation mode during the accident recovery period.
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3/4.5 EMERGENCY CORE COOLING SYSTEMS (ECCS)
BASES 3/4.5.1 SAFETY lNJECTION TANKS The OPERABILITY of each of the Reactor Coolant System (RCS) safety injection tanks ensures that a sufficient volume of borated water will be immediately forced into the reactor core through each of the cold legs in the event the RCS pressure falls below the pressure of the safety injection tanks.
This initial surge of water into the core provides the initial cooling mechanism during large RCS pipe ruptures.
The limits on safety injection tank volume, boron concentration, and pressure ensure that the assumptions used for safety injection tank injection in the safety analysis are met.
The safety injection tank power operated isolation valves are considered to be "operating bypasses" in the context of IEEE Std. 279-1971, wh'ich requires that bypasses of a protective function be removed automatically whenever permissive conditions are not met.
In addition, as these safety injection tank isolation valves fail to meet single failure criteria, removal of power to the valves is required.
The limits for operation with a safety injection tank inoperable for any reason except an isolation valve closed minimizes the time exposure of the plant to a LOCA event occuring concurrent with failure of an additional safety injection tank which may result in unacceptable peak cladding temperatures.
If a closed isolation valve canno' be immediately opened, the full capability of one safety injection tank it not available and prompt action is required to place the reactor in a mode where this capability is not required.
3/4.5.2 and 3/4.5.3 ECCS SUBSYSTEMS The OPERABILITY of two separate and independent ECCS subsystems ensures that sufficient emergency core cooling capability will be available in the event of a LOCA assuming the loss of one subsystem through any single failure consideration.
Either subsystem operating in conjunction with the safety injection tanks is capable of supplying sufficient core cooling to limit the peak cladding temp.eratures within acceptable limits for all postulated break sizes ranging from the double-ended break of the largest RCS cold leg pipe downward.
In addition, each ECCS subsystem provides long-term core cooling capability in the recirculation mode during the accident recovery period.
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J hSELT d with RCS temperature above 500 F two OPERABLE ECCS subsys-tems are required to ensure sufficient emergency core cooling capability is available to prevent the core from becoming critical during an uncontrolled cooldown (i.e., a steam line break) from greater than 500*F.
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